In recent years, researches have been conducted on quinolone derivatives of the formula (I) which have a wide spectrum of applications as a fungicide.
Korean Patent Publication No. 87-895 discloses a process for preparing quinolone derivatives of the formula (I) by heating under reflux a dihaloquinolone of the formula (II) in the presence of dry piperazine and dimethyl sulfoxide (DMSO) at 135.degree. C. to 140.degree. C. ##STR5## in which R.sub.1 is the same as defined for R.sub.1 in the formula (I) and X represents halogen.
Alternatively, Korean Patent Publication No. 87-1944 discloses a process for preparing such compounds which comprises heating with stirring a dihaloquinolone in the presence of dry piperazine at 115.degree. C. for 5 hours.
The prior arts heretofore mentioned require elevated reaction temperatures and long reaction time, providing a great deal of energy consumed while they employ solvents of high boiling point only to fail a successful solvent recovery. In addition, time consuming reaction at elevated temperature would cause undesirable by-products which eventually give low yield of the product.